T-5

Recent Progress and Subjects of Plasma Applications
最近のプラズマ応用の進展と課題
Hiroshi Fujiyama
藤山 寛Graduate School of Science and Technology, Nagasaki University
1-14, Bunkyo, Nagasaki 852-8521, Japan
長崎大学生産科学研究科，〒852-8521 長崎市文教町1-14
Plasma has been widely used in various scientific and industrial fields for more than 30 years. In recentyears, control of plasma processing for materials synthesis has become difficult because of technologicalproblems and practical needs: low-temperature, annealing-free, damage-free, high-rate & low-cost,vacuum-free, green process, maintenance-free processes et al. From the scientific point of view, it isrequired to investigate on plasma induced subsurface just under the surface of depositing or etching layers.

1. Intr oduction
Application of the forth state of matter: plasma
has been widely used in the various industries. In
recent years, people can usually hear the word
“Plasma” such as Plasma TV, Plasma cleaning,
Plasma engine etc. Thus, plasma technologies areuseful in the various industries such as Energy,Electronics, New Materials, Environment, Biology
and Nanotechnology. However, we must find that itis not a “Plasma Industry” in spite of their principal
or indispensable role for these industries.
Here, we will discuss about newly constructing
plasma induced subsurface science for more
intelligent plasma process in the 21st Century.
2. Plasma Application Technology
Figure 1 shows the tree of plasma application
based on plasma science. In addition to theconventional fields such as Light Sources, Energyand Semiconductor, new applications of plasma inthe fields such as Biology, Nanotechnology andEnvironmental are increased.
AtomicFusion

Beams
Light Sources
Displays

Laser
UV/EUVSpace

PlasmaPropulsion

Solar Cells

Wide
Plasma Applications
Fine
Chemical Analysis

Cleaning／Purification
Exhaust Gas, VOC

Environment

Etching
Deposition(Low-k F ilms,Gas Barrier ）Plasma Science
GaseousElectronics

3. Subjects for Plasma Processing
Figure 2 shows a lot of research subjects forplasma deposition such as PACVD and Plasma
PVD. As the technological problems and/or
practical needs, it should be nominated that lowtemperature, annealing-free, damage-free, high-rate& low-cost, vacuum-free, green process without
environmental damage, maintenance-free processes.
Especially, an annealing-free low-temperaturedeposition process is strongly required for use offlexible substrates.
For more precise control of desirable film quality,
we should collect the real information about“subsurface” under depositing or etching layer on
the substrate. Subsurface including the plasma-wall(solid, liquid) interactions under a processing is themost important subject.

Subjects for Plasma Deposition

New Energy

Welding/Cutting

Plasma Display
Lamps

We must note that it takes around 15 years ormore to put a research idea to practical use, forexample, Plasma Display Panel.

New Materials
Nanotechnology

DiamondF ullerenes(C60, C70…)
Carbon Nano Tube
Super Conductor
Magnetics, MEMS

Surface Treatment
Sterilization

Low -cost

Atm osph ericHigh Density Plasm aElectr ode
TargetNano-co mpo sit Film s

Large-area+ -ReactiveGases

Inverse Sputtering

Semiconductor
Electronic Device

Substr ate

Low -dam age
SurfaceScience-C ha rged Particles
Pho to n+- +-M ete r-size++-+Plasmas+Pu rifi ca ti on+ N anoparticles
Dust R em ova lSubsurface
ControlRadicals++ - + -High -ra te Etch ing& Ashin gThin Film Transistor
VLSI ・Memory
Organic Device

Fig. 1 The tree of plasma applications

Co nform al

Low -te m perature
Crystalli za ti on

Hi gh-rate D eposition

MedicalBiology

AtomicSpace
Chemistry
Applied Physics
Physics
Physics
Materials
Quantum
ScienceElectromagnetic
VacuumNagasaki UniversityMechanics

3-D D epositi on

RF Source

A tmo spheric P lasm aFunctional
Thin Films

Substrate Heater

Control ofCrysta llization/
Orie ntati on

Low -tem perature
Po lym er / Plastics
Substrate

Nagasaki University

Fig. 2 Subjects for plasma deposition

VacuumPumps

4. Plasma Induced Subsur face Science4.1 Subsur face Str uctur e“Subsurface” is just depositing or etching layerswith several nm ~ several 10nm thicknesses, as
shown in Fig. 3. This figure shows the subsurface
reaction during beam etching on Si substrate by
Molecular Dynamics (MD) Simulation by S.
Hamaguchi. The structure near surface of etchinglayer is also shown in this figure. There are twoparts of gas-phase and solid phase subsurface
regions. Plasma induced subsurface seems to beliquid-phase before solidification.
PlasmaSheathGas-phase
Subsur faceSur face
Solid-phase
Subsur face(nm~sever al 10nm)

Substr ate(Bulk)

Nagasaki University

Fig.3 Subsurface structure induced by reactive plasma

4.2 Plasma Induced Subsur face Science
To control subsurface reactions in reactive
plasmas, we should firstly measure subsurface
parameters such as the temperature, particle fluxand energy, photon flux, transport ratio and reaction
time etc. Infrared absorption spectroscopy (IRAS)
in multi internal reflection is one of useful method
to diagnose the solid-phase subsurface parameters.
Computer simulation such as MD is useful tool
to design the model of subsurface reaction.
Plasma Induced

Subsurface Control
Multi Par ticle Beam

Diagnostics

Selective Injection
Charging
Energy, Flux

Nanopar ticles
For mationin Gas Phase

LIF, IR, ATR
IR Laser Absor ption

Diagnostics

Nucleation
Size Contr ol
Transpor tSolid-phase
Subsur face

Semiconductor
Process
3-D SIP
Silicon-Diamond Device
Or ganic EL
Low-K, High-K

Gas-phase
Subsur face

Car bon Mater ial
Pr ocess

Modeling /Simulation

Low-temper atur e
Cr ystallization
Subsur face Excitation

Fuleren, CNT,Diamond

Gas Phase
Cr ystallizationof Nanopar ticles(Magnon, Phonon, mm Wave， Transport & Attachment
Pr ocess to Substr ate
Super Sonic, Ions・・・）

Control

Fig. 4 Approach to plasma induced subsurface science

Figure 4 shows the example of research subjects
to approach “Plasma Induced Subsurface Science”.
The author is interest in low temperature
crystallization by direct excitation of solid-phasesubsurface by magnon, phonon, mm-wave andsupersonic wave etc.
5. Conclusion
Recent subjects of plasma application, especiallyplasma processing, was discussed. Plasma induced
subsurface is most important reactive layer underconstruction of thin film deposition and etching.
To precise control of film quality, it is expected
the understanding of subsurface induced by reactive
plasmas.
Acknowledgments
The author would like to thank all the members of
Subsurface Research Group for their fruitful discussion
and help.